The increasingly arcane methods people must resort to to getting fiat into the market (since mining is quickly becoming solely the territory of an elite few) are very worrisome. The fact that for most US residents there are only a couple of reliable channels for conversion is a blatant achilles heel for the market (its not much better for EU).

IMO, the real existential threat to BTC isn't the government going after BTC itself, its them completely shutting down the exchange market. It would be alarmingly easy to accomplish this given the current market infrastructure.

For the health and long term stability of Bitcoin, the exchange problem must be solved. The current system (Gox + a few hangers on [vircurex btc-e]) does not have a good long term prognosis.